The present invention relates to the projecting construction method and apparatus for molten-metal-discharging holes of converter tapholes, vacuum degassing furnaces, etc., and a projection impeller for concave sections used in said apparatus. The present invention has application in the repairing, constructing, and forming of a molten-metal-discharging hole by projection.
For example, the inside wall of a converter taphole which is one example of a molten-metal-discharging hole is lined with refractory material. In proportion to its use, this refractory material gets damaged or becomes worn-out and requires repair. As a method of repairing this damage or wear in a hot state, there have been techniques such as the pressing injection repairing method the , spray repairing method, and the projection repairing method.
The above-said pressing injection repairing method is a technique for filling a cylinder with flowable repairing material and pushing it out by piston, which results in a poor rate in the adhesion of repairing material onto a conically-worn-out section ( also called a bell-shaped worn-out section) on the inside wall of above-said converter taphole. Even if the repairing material adheres onto the section, no usable structure forms at the repaired section.
The spray repairing method is a technique for spraying repairing material through the spraying nozzle of a spraying lance onto a section to be repaired by means of compressed air. This method has had problems that the effect in adhesion of the repairing material is poor and the structure of the repaired section is also poor due to the influence of the compressed air used to transfer the repairing material if enough clearance is not secured between the spraying nozzle and the inside wall of the converter taphole.
In the case of the spray repairing method, there has been another problem that spraying onto the conically-worn-out section 10 inside the converter taphole as shown in FIG. 11 becomes impossible due to the clogging of repairing material at the bent section between the spraying lance 12 and the spraying nozzle 11, if the spraying nozzle 11 is attached to the spraying lance 12 with such angle that the repairing material may be sprayed at an acute angle (.theta. is smaller than 90 degree).
Further, in the case of the projection repairing method, it is possible to repair the converter taphole by use of an apparatus for repairing a molten metal degassing equipment such as that disclosed in the Japanese Utility Model No. 1432690 (published in the gazette of the second publication No. 56-82513) and, as shown in FIG. 12. The repairing apparatus 17 published in above-said gazette is provided with a rotating tube 19a and a vertical tube 19 connected to the rotating tube 19a at the bottom center of the rotating impeller 18, wherein the refractory material supplied via the vertical tube 19 is ejected through the periphery of the impeller 18.
However, in the case of the above-said apparatus 17 for repairing molten metal degassing equipment, there has been a problem that the refractory material is discharged only by the centrifugal force which is generated accompanying the rotation of the impeller. As a result, enough dispersing speed cannot be obtained because the refractory material is supplied from the central vertical tube 19 to the rotating tube 19a connected to the center section of the impeller.
Another problem is that it is impossible to obtain a well-lined layer at a conically-worn-out section with a slope because the refractory material is dispersed only in the direction perpendicular to the impeller. Therefore it is difficult to disperse the refractory material perpendicularly onto the sloped conically-worn-out section.
Further,there has been a problem that the refractory material is dispersed evenly only in the radial direction. It is difficult to eject the refractory material in a limited direction and, therefore, it is difficult to efficiently repair a worn-out section generated only in a limited direction of a converter taphole. Moreover, in the case of the apparatus 17 for repairing molten metal degassing equipment published in the gazette, the repairing function can be lost due to the clogging of the material at the joint section between the rotating tube 19a and the impeller 18.
The present invention has been made in view of above-described circumstances and, accordingly, it is an object of this invention to provide a projecting construction method and apparatus for molten-metal-discharging hole and a projection impeller for concave section used in said apparatus for projecting the projection material onto a concave section. It is thus possible to increase the material-projecting speed so as to improve the adhering force of the material. As the case may be, it is also possible to project the projection material (including refractory and other repairing materials) in the limited direction to enable an effective repair on a molten-metal-discharging hole having an eccentric or a partial wear. It is further possible to perform construction with high-adhesion and a fine structure at a conically-worn-out section (a concave section of a molten-metal-discharging hole) generated on the inside wall of a converter taphole.